Field of the Invention
The present technique relates to a photoelectric conversion device including a metal oxide semiconductor (MOS) transistor.
Description of the Related Art
In a photoelectric conversion device, such as an image sensor, millions to tens of millions of pixel circuits are arranged, and a signal from the pixel circuit may be used as a pixel signal. Expansion of an area of a light receiving region of a photoelectric conversion element is effective to improve a sensitivity and a saturated electron amount of the photoelectric conversion element. In order to expand the area of the light receiving region of the photoelectric conversion element, it is necessary to reduce an area other than the light receiving region of the pixel circuit.
In a paragraph 0025 of Japanese Patent Application Laid-Open No. 2013-84740, it is described that a first contact plug (321) connected to a transfer gate electrode (121) is arranged on a first active portion (2A) such as on a channel region.
In miniaturization and a layout change of devices in the pixel circuit, there are restrictions in manufacturing processes of the photoelectric conversion device and in characteristics of an MOS transistor in the pixel circuit. When a contact plug is arranged on a channel region as in the case of Japanese Patent Application Laid-Open No. 2013-84740, there is a possibility of deteriorating characteristics of a transistor. The present technique is directed to improvement in performance of a pixel circuit.